Process and system for recovery of asphaltene by-product in paraffinic froth treatment operations

ABSTRACT

A process for treating bitumen froth with paraffinic solvent is provided which uses three stages of separation. Froth and a first solvent are directed to a first stage at a solvent/bitumen ratio for precipitating few or substantially no asphaltenes. A first stage underflow is directed to a second stage and a first stage overflow is directed to a third stage. A second stage underflow is directed to waste tailings and the second stage overflow joins the first stage overflow. A third stage underflow is recovered as an asphaltene by-product and a third stage overflow is recovered as a diluted bitumen product. At least a second solvent is added to one or both of the second or third stages for controlling a fraction of asphaltenes in the third stage underflow. Asphaltene loss to waste tailings is minimized and asphaltenes are now recovered as asphaltene by-product.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/582,662, filed Oct. 20, 2009 (allowed), which was anon-provisional application based on U.S. Provisional Patent ApplicationSer. No. 61/107,617, filed Oct. 22, 2008, both of which are incorporatedby reference in their entirety.

FIELD OF THE INVENTION

The invention relates to the separation of bitumen, solvent, water,solids and asphaltenes in a paraffinic froth treatment process. Moreparticularly, solvent is added to the influent of each of at least twostages of three stages of separation. The overflows of the first andsecond stages combine at the third stage for recovery of a dilutedbitumen product stream and an asphaltene by-product stream.

BACKGROUND OF THE INVENTION

Recovery of bitumen from mined oilsands involves separation of abitumen-rich froth from an oilsand slurry, and treatment of the froth toremove impurities and produce a marketable product. Known paraffinicfroth treatment processes involve the addition of a paraffinic solventto the bitumen-rich froth which enables separation of the mineral andwater contaminants and production of a marketable bitumen product.Asphaltenes in the bitumen precipitate if sufficient paraffinic solventis mixed with froth. In a froth settler vessel the precipitatedasphaltenes settle along with the mineral and water contaminants. Thisgravity settling process separates the diluted froth into two streams; adiluted bitumen product at a top and an underflow at a bottom. Theunderflow is a mixture of solids, water, bitumen, solvent andprecipitated asphaltenes.

Typically, the paraffinic froth treatment process can be sub-dividedinto three components: froth settler/separation, solvent recovery andtailings solvent recovery. After the froth settling/separation, thediluted bitumen product is sent to a solvent recovery unit (SRU) wheresolvent is recovered for re-use and clean bitumen is obtained as thefeed to an upgrading process. Underflow from froth settling/separationis sent to a tailing solvent recovery unit (TSRU) to recover residualsolvent.

Conventional settler/separation operations implement a counter-current,multi-stage system to produce two streams, a solvent-rich dilutedbitumen product (which includes some asphaltenes), and an underflowtailings stream containing solids, water, bitumen, solvent andprecipitated asphaltenes.

In a solvent recovery unit (SRU), a distillation column is employed forrecovering relatively volatile solvent from the solvent-rich dilutedbitumen product and delivering a clean, solvent-free, bitumen productand solvent stream for reuse.

In a tailings solvent recovery unit (TSRU), residual solvent in thesettler underflow stream is recovered to ensure that a final tailingsstream contains minimal amounts of residual solvent. Conventionally, aTSRU vessel is a flash tower into which the hot, pressurized tailingsstream is released, resulting in rapid vaporization of the bulk of theresidual solvent from the tailings. Steam may be added to furtherscavenge solvent from the tailings.

Two prior art processes which implement counter-current processes areCanadian Patent application 2,454,942 to True North Energy and Canadianpatent 2,521,248 to Shell et al.

CA 2,454,942 describes a process in which a low-molecular weightparaffin is used as the solvent in a two-stage settler configuration.Underflow from a first stage settler is directed as influent to a secondstage settler. In this process, the only introduction of solvent is byaddition to the influent of the second stage settler, and the secondstage settler overflow is recycled to the influent of the first stagesettler. The overflow product of the first stage settler is the finalproduct to the SRU. Accordingly, solvent is only added to the firststage settler by recycling back from the second stage settler overflow.The process is known as a counter-current process as the solvent flowscounter-currently to the flow of froth. The second stage underflow isthe influent to the TSRU.

CA 2,521,248 describes a process which applies three settlers. As in theTrue North process, there is a recycling of the overflow from the secondstage settler to the influent of the first stage settler. The secondstage overflow contains mainly solvent and diluted bitumen. Further, theoverflow of the third stage settler is recycled back to the influent ofthe second stage settler. The overflow product of the first stagesettler is the final product to the SRU. The only introduction ofsolvent is by addition to the influent of the third stage settler, andtherefore solvent is only recycled to the first and second stagesettlers by recycling back from the third stage settler. Again, acounter-current process is described with the overflow product of thefirst stage settler being the final diluted bitumen product to the SRUand the third stage underflow being the influent to the TSRU.

Other than the diluted bitumen product stream, each of the True Northand Shell processes result in a single, high water content waste streamfor downstream processing in the TSRU. The True North process results inabout 7% of the bitumen in the froth being precipitated as asphaltenesand lost to the tailings. Asphaltenes are not a desirable component in atailings stream or the bitumen product stream.

There is a need for recovering at least some of the asphaltenesotherwise lost to the tailings for reducing environmental impact, or forother beneficial purposes. Further, improved handling of the asphaltenesfraction can result in reduced asphaltene content in the diluted bitumenproduct. Simply, there are synergistic objectives to reduce hydrocarbonloss in tailings and to recover a valuable product from what isotherwise wasted.

SUMMARY OF THE INVENTION

The present invention provides a system, process and arrangement ofseparator stages and staged solvent addition which redirects asphaltenespreferentially from waste tailings to a new asphaltene by-productstream. As a result, the waste tailings contain a lower proportion ofasphaltenes than heretofore achieved. Much of said asphaltenes arerecovered in the asphaltene by-product stream that were otherwise lostto waste tailings in the prior art processes.

Paraffinic solvent is known to precipitate asphaltenes from bitumenfroth. However, as disclosed herein, it has been discovered that use ofcontrolled and multiple points of addition of paraffinic solvent, splitbetween multiple stages of separators, and the arrangement of theseparators cooperate to control the precipitation.

In embodiments of froth treatment disclosed herein, at least threestages of separation are provided. A first stage and a second stage arearranged in series, the underflow of the first stage flowing as influentto the second stage. The overflows of the first and second stages arecombined as the influent to a third stage. Paraffinic solvent is addedto the influent of the first stage and to the influent of at least oneof the second or third stages. The solvent to bitumen ratio (S/B ratio)is controlled. As a result, three product streams are recovered: a wastetailings from the underflow of the second stage which is high in waterand low in hydrocarbon fractions, a solvent-diluted bitumen stream fromthe overflow of the third stage and an asphaltene by-product stream fromthe underflow of the third stage which is also low in solids and low inwater fractions. As asphaltene is a constituent of the bitumen, therecovery of bitumen in the diluted bitumen stream may be reducedslightly as asphaltenes are precipitated and redistributed between thewaste tailings and asphaltene by-product stream. The precipitation ofasphaltenes from the froth yields an improved quality or cleanliness ofthe diluted bitumen.

Simply, the embodiments herein manipulate asphaltene precipitation tobest advantage. For example, solvent addition to the first stage canresult in precipitation of asphaltenes which are lost to waste tailings,however, some asphaltene precipitation also aids in water and solidsseparation from the froth. Further, in an embodiment adding solventaddition to the second stage, asphaltenes can precipitate from bitumenin the first stage underflow and be lost to waste tailings, but willalso result in additional recovery of bitumen from the second stageoverflow for delivery to the third stage. All bitumen, includingasphaltenes, reporting to the third stage is now recoverable. An overallS/B ratio achieved by confluence of at least the first and second stageoverflows at the third stage, and optionally of a third stage solventaddition. This overall S/B ratio aids in the precipitation ofasphaltenes for further asphaltene-cleaning of the bitumen for recoveryas a dilute bitumen product and recovery of the precipitated asphaltenesas an asphaltene by-product.

In one embodiment, the paraffinic solvent is split between the first andsecond stages. Paraffinic solvent is added to the first stage in an S/Bratio which is below or in the vicinity of about a conventionalasphaltene precipitation threshold. On the other hand, when paraffinicsolvent is then added to the second stage, as a result of the influentto said second stage having a reduced bitumen fraction, this secondsolvent addition S/B ratio is much higher than a conventional asphalteneprecipitation threshold.

In embodiments, the overall S/B ratio for the system remains comparableto that applied in conventional counter-current processes, however,having been applied in several stages.

In another embodiment, solvent is added to the influent of the firststage and to each of the influents of the second and third stages ofseparation.

Each stage of the separation can be conducted in conventional frothsettlers. Alternate separators include centrifuges and hydrocycloneswhere appropriate. Centrifuges could be particularly suited at the firststage.

Accordingly, in one aspect of the invention, a process for treatingbitumen froth comprises: directing the froth and a first paraffinicsolvent as a first influent to a first stage separator. A firstunderflow from the first stage separator is directed to a second stageseparator. A first overflow from the first stage separator is combinedwith a second overflow from the second stage separator as a thirdinfluent to a third stage separator. A second underflow is produced fromthe second stage separator as a waste tailings. At least a secondparaffinic solvent is added to at least one of the second influent orthird influent. Finally, a third overflow from the third stage separatoris produced as a diluted bitumen product, and a third underflow from thethird stage separator is produced as an asphaltene by-product.

In one embodiment, the at least a second paraffinic solvent is a secondsolvent added to the second influent. In another embodiment, the atleast a second paraffinic solvent is a second solvent added to the thirdinfluent. In yet another embodiment, the at least a second paraffinicsolvent comprises two solvent additions: a second solvent added to thesecond influent and a third solvent added to the third influent.

The first paraffinic solvent is added for precipitating little orsubstantially no asphaltenes, thereby minimizing losses to tailings. Theat least a second paraffinic solvent is added to control the fraction ofasphaltene reporting at the third underflow. Hydrocarbon loss isminimized at the waste tailings and overall bitumen recovery ismaximized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of an embodiment of a froth treatment processof the present invention having two stages of solvent addition; and

FIG. 2 is a flow diagram of an embodiment of a froth treatment processof the present invention having three stages of solvent addition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Paraffinic solvent is added to a bitumen-rich froth which enablesseparation of the mineral and water contaminants and production of amarketable bitumen product. Paraffinic solvent is admixed with froth andintroduced to a froth separator. The solvent dissolves in the bitumenfraction of the froth. An amount of solvent added is typically referredto in terms of a solvent to bitumen ratio (S/B ratio).

Conventionally, sufficient paraffinic solvent is added to the froth toprecipitate asphaltenes. The diluted solvent/bitumen hydrocarbon phaseis less dense than the mineral, water and precipitated asphaltenes.Further, during the separation process, precipitated asphaltenes havethe beneficial effect of capturing incremental mineral and water thatwould otherwise not have been separated out of the hydrocarbon phase.Generally speaking, the greater the asphaltene precipitation, thecleaner will be the diluted bitumen product obtained after theseparation is complete, this cleaner diluted bitumen product having alower asphaltene content.

In an embodiment of the invention, a flow-through froth treatmentprocess comprises a process and system for introducing paraffinicsolvent to bitumen-rich froth and separating a solvent-diluted bitumentherefrom in at least three stages of separation, one result being theformation of a new, asphaltene by-product stream.

In the embodiments described herein, each of multiple stages ofseparation may also be referred to as settlers, although otherseparation processes could also be employed including centrifuges andhydrocyclones. Accordingly, except where the context is expresslyotherwise, the term “settlers” is also to be read broadly as a separatorwhich happens to include at least settlers, centrifuges andhydrocyclones.

Having reference to FIG. 1, froth F is directed as a part of a firststage influent or first influent 5 to a first stage separator 10. Afirst solvent S1 is added to the froth F to form part of the firstinfluent 5. A first underflow 12 from the first stage settler 10 isdirected to form part of a second stage influent or second influent 15to a second stage settler 20.

A second solvent S2 is added to the first underflow 12 and forms part ofthe second influent 15 to the second stage settler 20. A secondunderflow 22 from the second stage settler 20 is produced as a wastetailings T.

A first overflow 11 from the first stage settler 10 is directed to formpart of a third stage influent or third influent 25 which is directed toa third stage settler 30.

A second overflow 21 from the second stage settler 20 is also directedto and forms a part of the third influent stream 25 to the third stagesettler 30.

A third overflow 31 from the third stage settler 30 is produced as adiluted bitumen product P.

A third underflow 32 from the third stage settler 30 is produced as anasphaltene by-product A.

The introduction of an asphaltene by-product A permits the process tocontrol asphaltene distribution. The prior art is constrained to balancethe need for asphaltene precipitation between competing objectives. Onone hand, the prior art encourages precipitation of asphaltenes to aidin froth separation but, on the other hand, precipitated asphaltenes arelost with the tailings. In CA 2,454,942 at page 24, it was recognizedthat since asphaltenes are essentially hydrocarbons, their precipitationduring the separating step should be managed to minimize loss ofhydrocarbons from the diluted bitumen component and to minimize theamount of precipitated asphaltenes which are contained in the tailingscomponent. The process disclosed in CA 2,454,942 limited theirimplementation of those objectives.

Herein, asphaltene precipitation can now be controlled so as to aid infroth treatment and yet also to redistribute precipitated asphaltenesfor reducing losses in the waste tailing T and recovering precipitatedasphaltenes in the new asphaltene by-product A. Further, the dilutedbitumen product P is cleaner, having been liberated of some asphaltenes.Further, the asphaltene by-product stream A happens to be characterizedby a low water and low mineral content.

Herein, any one or more of the first, second or third stage settlers10,20,30 can comprise one or more physical separators to meet theprocess requirements. Conventional separation vessels can be employedincluding settlers such as vertical and inclined plate settlers. Otherseparation vessels include centrifuges or hydrocyclones.

In an embodiment of the invention, the waste tailing stream T isdirected to a tailing treatment process such as a TSRU. The dilutedbitumen product P is directed to a SRU. The asphaltene by-product streamA is directed for further processing or use.

As shown, solvent is added in at least two stages, the first solventstream S1 being added to the froth F as part of the first influent 5 tothe first stage settler 10. The second solvent stream S2 is added to atleast a further stage, shown in FIG. 1 as forming part of the secondinfluent 15 directed to the second stage settler 20. The adding of asecond paraffinic solvent S2 to the second influent 15 comprisescontrolling a fraction of asphaltene reporting at the third underflow 32from the third stage settler 30.

The combined, target or overall S/B ratio, that is (S1+S2)/B, providedto the froth treatment operations, can be conventional as is known bythose of skill in the art. Various ranges of S/B ratios are known forother paraffinic froth treatment processes and which are dependant uponvarious parameters including the grade of the bituminous ore, theparticular paraffinic solvent being used and the temperature of theoperations. Known paraffinic solvents include C4 though C7, variousmixtures thereof and natural gas condensate which includes alkanes of C5through C16.

Again, as set forth in CA 2,454,942, one view is that asphaltenes tendto exhibit greater solubility in longer chain paraffinic solvents thanin shorter chain paraffinic solvents, with the result that the amount ofasphaltenes precipitated decreases as the selected paraffinic solventbecomes heavier or longer chained. Asphaltene precipitation is thereforegenerally greater in pentane than it is in hexane, heptane or octane.The precipitation of asphaltenes from the bitumen froth stream is alsodependent upon the selection of the operating temperature for theseparating step. The amount of asphaltenes precipitated from aparticular solvent will generally decrease as the operating temperatureis increased. Finally, the precipitation of asphaltenes from the bitumenfroth stream is also dependent upon the amount of diluent solvent whichis added to the bitumen froth stream. The amount of asphaltenesprecipitated from a particular solvent will generally increase as theamount of the solvent, S/B ratio, increases.

A common and conventional range of overall S/B ratio is about 1 to about2.

In the embodiment of FIG. 1, the solvent S1,S2 is introduced as part ofthe first and second influents 5,15 respectively and the total solventis therefore split between the first and second stage settlers 10,20.The amount of solvent S1,S2 added is controlled through the control ofthe S/B ratio.

The first solvent S1 is added to the bitumen froth F and the mixtureforms the first influent 5 to the first stage settler 10. The amount ofthe first solvent S1 is controlled in order to have an S/B ratio below,up to or in the vicinity of about an asphaltene precipitation threshold.In prior art processes, a typical S/B ratio would be selected so as tobe at or above an asphaltene precipitation threshold, for example atabout 1.5 for the conventional two-stage, counter-current frothtreatment process. The prior art process has one opportunity, at thefirst stage vessel, to recover a diluted bitumen product. Greater S/Bratios are known to result in greater asphaltene precipitation.

Herein, in contrast to the prior art processes, one embodiment appliesan S/B ratio of the first solvent S1 at a first addition S/B ratio whichis non-zero and can be up to and about the asphaltene precipitationthreshold for the conditions present at the first stage settler. Incontra-distinction to the prior art, this approach results in little orsubstantially no asphaltene precipitation. In the exemplary embodimentof FIG. 1 and corresponding Examples A, B, C and D, using substantiallypentane as the first stage solvent S1, the first addition S/B ratioranges from about 0.7 to about 0.9.

Consequently, the first stage settler 10 produces a first underflow 12containing mainly solids, water, with a small amount of bitumen, and thepossibility of a small amount of precipitated asphaltenes. Most of thewater and solids are separated or dropped out, at least in part as aresult of the first solvent S1. As discussed, the first additional S/Bratio is generally lower compared to the prior art and the asphalteneprecipitation threshold. The first overflow 11 produced by the firststage settler 10 contains diluted bitumen, water, and solids. Thediluted bitumen includes any asphaltenes not reporting to the firstunderflow 12.

The second solvent S2 is then added at a second addition S/B ratio tothe first stage settler's first underflow 12 and the mixture is directedas second influent 15 to the second stage settler 20. As the amount ofdiluted bitumen remaining in the first underflow 12 is already low, thelow magnitude of the bitumen denominator results in a second additionS/B ratio, entering the second stage settler 20, which is very high.Consequently, a large fraction or substantially all the residualasphaltenes in the bitumen flowing to the second stage settler 20 areprecipitated. Precipitated asphaltenes are removed with the secondunderflow 22 to the waste tailings T along with essentially all themineral and water entering the second stage settler 20. In thisembodiment, the amount of solvent S2 added in the second stage settler20, the second addition S/B ratio, is adjusted to control the rejectionof asphaltene from the overall process.

The first and second overflows 11 and 21 from the first and second stagesettlers 10,20 respectively are combined and directed as the influentstream 25 to the third stage settler 30 with an overall S/B ratio whichis at about conventional S/B ratios. For paraffinic solvents which aresubstantially pentane, the overall S/B ratio is about 1.25 or could behigher.

As a result, the water and solids content in the third stage underflow32 is low, and the asphaltenes therein are recoverable in the asphalteneby-product A.

With reference to FIG. 2, in an optional embodiment, a third stream ofsolvent S3 could be added to form part of the third stage influentstream 25. Solvent S3 is added so as to more finely manage asphalteneprecipitation and control the asphaltene by-product stream A from thethird settler 30. The second addition S/B ratio is reduced toaccommodate a third addition S/B ratio, the overall S/B ratio(S1+S2+S3)/B still being about conventional for known paraffinic frothtreatment operations.

The water content in the third settler underflow 32 can be controlled bycontrolling the S/B ratios in each of the first and second stagesettlers 10,20, and optionally the third stage settler 30. For example,if it is desirable to reduce water and solid content, more solvent S1can be added in the first stage settler 10. If more asphalteneprecipitation is desired, the S/B ratio at the third influent stream 25to the third stage settler 30 can be increased by adjusting the solventS2 addition to the second stage settler 20, or also by adding theoptional solvent S3 to the third influent 25 of the third stage settler30.

Test results have shown that water and solids content in the third stagesettler underflow 32 can be about 25% or less which means that, having ahydrocarbon content contributed mostly by asphaltene and residualsolvent, this asphaltene by-product stream A can be used as fuel eitherbefore or after additional processing to remove solvent and/or water.

EXAMPLES

Bitumen comprises maltenes and asphaltenes. Froth F comprises bitumen,water and minerals. All percentages are in weight %.

Exemplary samples used in testing were as follows in Table 1:

TABLE 1 Froth for Examples A-E Examples A, B, C D, E Component wt % wt %Bitumen 67.4 57.2 Water 23.8 34.7 Mineral 8.8 8.1 Total 100.0 100.0 Ofthe bitumen in the froth, 17.9 19.5 % asphaltenes

Laboratory programs were conducted to assess different locations formultiple solvent addition and the effect on the redistribution ofasphaltenes.

Examples A, B and C

Table 2 outlines the parameters in the paraffinic tests for theembodiment shown in FIG. 1 and Tables 2A, 2B and 3C present the results.The solvent used was substantially pentane and the tests were conductedat 80° C. Each test happens to have been repeated using a demulsifierintroduced to the first stage without significant adverse or beneficialeffect.

TABLE 2 Examples A, B, C - Test Matrix for Paraffin Solvent S/B in eachstage based on FIG. 1 Overall S/B First stage Second Stage Target byThird 10 20 Stage 30 TEST S1/B S2/B (S1 + S2)/B A 0.7 11.5 1.25 B 0.89.8 1.25 C 0.9 5.5 1.25

Tables 2A, 2B and 2C report the recovery of the original bitumen in thefroth to the various products, rounded to the nearest 0.1%. For example,for Test A, the bitumen was recovered as follows: 88.6% to the dilutedbitumen product P, 1.7% loss to waste tailings T and the balance of 9.7%in the asphaltene by-product A, for a total of 100% of the bitumen inthe froth F. Asphaltenes are concentrated in the asphaltene by-productA. From Table 1, initially 17.9 wt % of the bitumen in the froth F wasasphaltenes. In Test A, of the 9.7% of the bitumen recovered in theasphaltene by-product A, 42.5% was asphaltenes.

TABLE 2A Examples A, B, C - Diluted Bitumen Product Diluted BitumenProduct P (Stream 31) Bitumen Water Solid S/B recovery Content ContentTEST 10 (%) (wt %) (wt %) A 0.7 88.6 <0.1 0.024 B 0.8 91.2 <0.1 0.021 C0.9 90.3 <0.1 0.048

TABLE 2B Examples A, B, C - Waste Tailings Waste Tailings T (stream 22)Bitumen Solvent Water S/B loss Content Content TEST 10 (%) (wt %) (wt %)A 0.7 1.7 2.9 82.8 B 0.8 2.0 2.7 93.5 C 0.9 3.7 0.3 86.0

It is understood that the prior art processes result in 8 to 10% of thebitumen reporting to the waste tailings stream, see J. H. Masliyah,“Extraction and Upgrading of Bitumen”, workshop Jun. 24 & 25, 2009,Calgary, p. B5-23. Examples A-C illustrate that bitumen loss to thewaste tailings is significantly reduced and, correspondingly,difficulties and environmental aspects are reduced also.

TABLE 2C Examples A, B, C - Asphaltene By-Product Asphaltene By-ProductA (Stream 32) Overall Asphaltene Bitumen Bitumen Content Water SolidsRecovery S/B Recovery (wt % of Content Content (31 + 32) TEST 10 (%)Bitumen) (wt %) (wt %) (wt %) A 0.7 9.7 42.5 18.5 6.5 98.3 B 0.8 6.840.9 20.0 5.2 98.0 C 0.9 6.0 41.3 18.9 5.8 96.4

The asphaltene by-product A is further characterized by a low water anda low mineral content. In the prior art, there is no asphalteneby-product A at all, and this otherwise recoverable bitumen isneedlessly lost to tailings.

As noted above, the asphaltene by-product A of Table 2C is combustible,having value as a fuel or other source of hydrocarbon.

Examples D, E

Tests for Examples D and E are additional tests performed at a differentlaboratory and using a different froth composition (see Table 1).Example D, like Examples A-C, has solvent addition to two stages ofseparation according to FIG. 1.

Example E is a test using solvent addition to all three stages ofseparation according to FIG. 2. It was expected that the use of solventaddition to the third stage settler 30 would further decrease the amountof precipitated asphaltene lost to the waste tailings T. Accordingly,the second addition S/B ratio to second settler 20 was decreased withthird addition S/B ratios of <3 targeted with the objective ofdecreasing the amount of asphaltene precipitated in the second stagesettler 20 and accordingly reporting to waste tailings T.

With reference to Tables 3A, 3B and 3C, the recovery of the originalbitumen in the froth 5 is illustrated for the various product streams22, 31 and 32.

TABLE 3A Examples D, E - Diluted Bitumen Product Diluted Bitumen ProductP (Stream 31) Bitumen Water Solid S/B recovery Content Content TEST 10(%) (wt %) (wt %) D 0.8 92.5 0.04 0.05 E 0.8 92.9 0.01 0

In this additional testing of Examples D and E, both the two-way splitsolvent addition and the three-way split solvent addition, respectively,produced comparable diluted bitumen recovery relative to Examples A, Band C.

TABLE 3B Examples D, E - Waste Tailings Waste Tailings T (stream 22)Bitumen Solvent Water S/B loss Content Content TEST 10 (%) (wt %) (wt %)D 0.8 2.9 8.11 70.1 E 0.8 4.1 17.7 62.8

Similarly, the Examples D and E consistently resulted in low bitumenlosses to the wasted tailings.

TABLE 4C Examples D, E - Asphaltene By-Product Asphaltene By-Product(Stream 32) A Overall Asphaltene Bitumen Bitumen Content Water SolidsRecovery S/B Recovery (wt % of Content Content (31 + 32) TEST 10 (%)Bitumen) (wt %) (wt %) (wt %) D 0.8 4.6 35.0 5.6 6.0 97.1 E 0.8 3.0 46.00.35 0.8 95.9

The water and solids content in the asphaltene by-product of Examples Dand E were consistently low, the overall recovery of bitumen at streams31 and 32 was comparable to those from Examples A, B and C, the overallrecovery of bitumen was improved over those recovered at the solediluted bitumen product stream of the prior art.

The embodiments of the invention for which an exclusive property orprivilege is claimed are defined as follows:
 1. A system for treatingbitumen froth with paraffinic solvent comprising: in a flow-throughprocess, a first stage froth treatment separator for receiving the frothand a paraffinic first solvent; a second stage froth treatment separatorfor receiving, as a second stage influent, at least a first underflowfrom the first stage separator and producing a waste tailings from asecond stage underflow; and a third stage froth treatment separator forreceiving a third stage influent of at least a first overflow from thefirst stage froth treatment separator and a second overflow from thesecond stage froth treatment separator, wherein at least a secondparaffinic solvent is combined with at least one of the second stageinfluent or the third stage influent, the third stage froth treatmentseparator produces a diluted bitumen product from a third stage overflowand produces an asphaltene by-product from a third stage underflow; thefirst underflow flows through to the second stage froth treatmentseparator to report as either the second overflow or the waste tailings,the first overflow flows through to the third stage froth treatmentseparator to report as either the diluted bitumen product or theasphaltene by-product; and the second overflow directly flows through tothe third stage froth treatment separator to report as either thediluted bitumen product or the asphaltene by-product.
 2. The system ofclaim 1, wherein the second stage influent comprises the at least asecond paraffinic solvent.
 3. The system of claim 1, wherein the thirdstage influent comprises the at least a second paraffinic solvent. 4.The system of claim 1, wherein the second stage influent and the thirdstage influent each comprises the at least a second paraffinic solvent.5. The system of claim 1, wherein the second stage influent comprisesthe at least a second paraffinic solvent and the third stage influentcomprises a third paraffinic solvent.
 6. The system of claim 5, whereinthe first paraffinic solvent, the at least a second paraffinic solventand the third paraffinic solvent are substantially pentane and whereinan overall solvent/bitumen ratio is about 1.25 or higher.
 7. The systemof claim 1, wherein the first paraffinic solvent and the at least asecond paraffinic solvent are substantially pentane and wherein anoverall solvent/bitumen ratio is about 1.25 or higher.
 8. The system ofclaim 1, wherein the first paraffinic solvent is added to the firststage froth treatment separator in a first addition S/B ratio forminimizing asphaltene precipitation in the first stage froth treatmentseparator.
 9. The system of claim 8, wherein the first addition S/Bratio is controlled between an S/B ratio below an asphalteneprecipitation threshold and an S/B ratio up to about the asphalteneprecipitation threshold.
 10. The system of claim 9, wherein the firstparaffinic solvent is substantially pentane and the first addition S/Bratio is non-zero and up to about 0.9.
 11. The system of claim 8,wherein the at least a second paraffinic solvent being added to thesecond stage froth treatment separator or the third stage frothseparator is controlled in order to control the fraction of asphaltenereporting at the third underflow.
 12. The system of claim 1, wherein theat least a second paraffinic solvent being added to the second stagefroth treatment separator or the third stage froth separator iscontrolled in order to control the fraction of asphaltene reporting atthe third underflow.
 13. The system of claim 1, wherein the first stageseparator, the second stage separator and the third stage separator aresettlers.
 14. The system of claim 1, wherein the first stage separatoris selected from the group of separators consisting of settlers,centrifuges and hydrocyclones.
 15. The system of claim 1, wherein thefirst stage separator, the second stage separator and the third stageseparator are selected from the group consisting of settlers,centrifuges and hydrocyclones.
 16. The system of claim 1, wherein thewaste tailings is substantially free of precipitated asphaltenes. 17.The system of claim 1, wherein at least the first stage and second stagefroth treatment separators are arranged in series.